1. Field
The present invention relates to handheld rangefinders for assisting a user in compensating for variables that affect projectile trajectory. More particularly, the present invention relates to a handheld rangefinder that utilizes a range sensor and a computing element to adjust stored hold-over values corresponding to a given range to compensate for an actual sight-in distance differing from a default sight-in distance.
2. Related Art
Hunters and other firearm and bow users commonly use handheld rangefinders to determine ranges to targets. Utilizing the displayed ranges, the hunter makes sighting corrections to facilitate accurate shooting.
For example, a rifle may be “sighted-in” or set for a particular range, such that the bullet strikes the target when crosshairs of a rifle scope are aligned with the target. But at distances greater than the sight-in distance, the bullet will be low on the target. Therefore, to compensate for this, the shooter must raise the rifle by an angle called “hold-over”. A rifle scope elevation adjustment assembly, such as described in U.S. Pat. No. 3,990,155 may be used to adjust the angle of the rifle by a specific hold-over value. Historically, handheld rangefinders fail to determine hold-over ballistic information corresponding to the amount by which hunters must vary their aim, thereby forcing hunters to manually perform hold-over calculations.
Additionally, slope and elevation may affect the projectile path of a bullet, such as when a hunter is positioned above or below a target. In such a situation, a bullet will hit the target higher than it would when the target is on the same elevation as the shooter.
Devices operable to compensate for slope and elevation utilizing lasers and inclinometers have been developed to alleviate some of these problems. Unfortunately, some of these devices have a limited field of vision, must be attached to a firearm, or are unable to provide hold-over ballistic information. Thus, hunters are unable to avail themselves of the beneficial aspects of handheld rangefinders, such as increased field of vision, maneuverability, and portability, while correcting for range, slope, elevation, and rangefinder orientation utilizing hold-over ballistic information.
Besides range, elevation, and slope, other variables can affect the hold-over value required for accurate aim, such as the particular projectile or firearm utilized as well as the distance at which a firearm is sighted-in. To determine the most accurate hold-over value, all of these variables should be considered. However, factoring all of these variable into manual hold-over calculations may not be practical or possible while hunting, since a target may not remain stationary for very long.